1. Field of the Invention
The present invention relates to a filter device provided in an air passage of an air conditioning device for removing foreign matter from air flowing through the air passage.
2. Description of the Related Art
Conventionally, many kind of filter devices are used for domestic air conditioning devices or vehicle air conditioning devices. For example, a filter device shown in Japanese Unexamined Patent Publication No. 59-89937 has plate-shaped filter elements connected by a hinge and able to bend relative to each other, so that the filter elements can be easily inserted in the air conditioning device.
Since the conventional filter element is made of, for example, a non-woven fabric, the filter element is not stiff, and therefore, a frame must be provided enclosing the periphery of the filter element, to maintain a predetermined shape thereof. Such a frame, however, increases a resistance to an air flow passing through the filter element, and further, the hinge member used for connecting the filter elements also causes an increase of the air flow resistance.